The hot surface of a circuit board is steadily dissipating heat at 8 w to the ambient air of 20 °c. the board itself is 15 cm wide and 20 cm long, and the heat loss on the other side of the board can be neglected. determine the average temperature of the hot surface when (a) the board is placed vertically (along 20-cm side), (b) the board is placed horizontally with the hot surface facing up, and (c) the board is placed horizontally with the hot surface facing down. assume the board surface has an emissivity of 0.8 and the surrounding surfaces are at 20 °c.

As we gain mass the force of gravity on us increases!

Answersystem;

Distance covered, s = 8ft - 4ft = 4 ftinitial velocity, u = 34 ft/sthe acrobat is moving upwards and therefore, a = -g = -9.81 m/s^2 = 32.19 ft/s^2applying equation of motion; s = ut -1/2gt^2then,4 = 34t -1/2*32.19t^24 = 34t - 16.095t^2rearranging; -16.095t^2 + 34t - 4 = 0solving the quadratic equation; t = {-34 +/- sqrt [34^2 - 4(-16.)]}/2(-16.095) = 1.06 +/- 0.93 = 0.13 or 1.99the acrobat will take 0.13 seconds to be at 8 ft above the ground. additionally, once at the maximum height, the acrobat will move down and be at the same spot (that is height) after 1.99 seconds moving down.